Filtration of tobacco smoke



United States Patent 3,498,299 FILTRATION OF TOBACCO SMOKE Ernest W. White, Fountain Valley, 'Califl, assignor to Wesley C. Bose Continuation-impart of application Ser. No. 576,958,

Sept. 2, 1966. This application Jan. 10, 1969, Ser.

Int. Cl. A2461 1/04; A24b 15/02 U.S. Cl. 131-265 11 Claims ABSTRACT OF THE DISCLOSURE This is a continuation-in-part of my copending application Ser. No. 576,958, filed Sept. 2, 1966, and now abandoned.

This invention relates to the filtration of tobacco smoke and more particularly to an improved filter material combination for removing certain harmful ingredients from tobacco smoke.

Over the years, various types of filters and filter materials have been proposed for filtering tobacco smoke. Separate filters which may be used in conjunction with cigarettes, pipes, and the like have been provided as well as various types of filter material actually mixed with tobacco. Filter cigarettes, for example, commonly employ a cellulose acetate filter, encircled by paper, and attached to an end of the cigarette. Some filters of this nature employ a combination of cotton and charcoal grandules. Various other materials, such as diatomaceous earth, bentonite, vermiculite, and others have been proposed for tobacco smoke filtration. Generally, only cellulose acetate filters, cotton and charcoal filters, and filters using water or moisture as a filtering or cooling medium have found any appreciable acceptance. Although these filters may be helpful in removing some constituents from tobacco smoke, they have not proven entirely satisfactory.

In filtering tobacco smoke, it is desirable to extract from the smoke each chemical component or group of components which are identified as carcinogenic, or otherwise undesirable, while passing only those components recognized as sources of the tobaccos unique taste and flavor, which are considered safe. Various types of materials and minerals which have proven effective in the filtration of oil had been proposed as tobacco smoke filters in an attempt to prevent or reduce the passage of tars and nicotine, which itself is a type of oil. Such materials and minerals have not proven satisfactory because they spoil the flavor of the tobacco, are injurious to health if inhaled, have not sufficiently acted as a heat shield between the burning tobacco and the mouth of the smoker, and have not efiiciently removed the tars or significantly removed the harshness found in tobacco smoke.

Research has disclosed that a number of poisonous gases such as hydrogen cyanide and acrolein areformed as a result of the combustion of tobacco and its components. Cigarette smoke, for example, is a heterogeneous mixture of gases, uncondensed vapors and liquid particulate matter. As the smoke enters the mouth of a human,

the smoke is a concentrated aerosol with millions or billions of particles per cubic centimeter having a median size of about .05 micron. Various gases, such as argon,

formaldehyde, hydrogen, cyanide, ammonia, propane,

butane, nitrogen dioxide, carbon dioxide and the deadly methane gas account for approximately sixty percent of the total cigarette smoke, and it will be apparent that a very efiicient type of gas mask filter for such smoke would be desirable.

Additionally, tobacco smoke produces polycyclic hydrocarbons which are known as carcinogens or cancer causing irritants. These include benzo(a)'pyrene, anthracene, acenaphthylene, and pyrene. Arsenic is present. Nicotine, of course, is present and is essentially an oil having an extremely small molecular chemical body, possibly one of the smallest found in nature. Contrary to accepted public knowledge, the Report of the Advisory Committee to the Surgeon General of the Public Health Service states that there is no acceptable evidence that prolonged exposure to nicotine creates either dangerous functional change of an objective nature or degenerative disease. This report concluded that the chronic toxicity of nicotine in amounts ordinarily obtained in common forms of to tobacco use is very low, and the nicotine is actively and rapidly metabolized by humans. The harm done to general health by smoking is caused by the many noxious poisons produced by the burning tobacco, cigarette paper, poisonous insecticides used in growing the tobacco and other materials added thereto.

In their separate actions on the health of the smoker, it has been found that the combination of the whole, gases and carcinogens, is more harmful than any of the known parts. Thus it is necessary to filter out enough of the particulate matter and gaseous composition of the smoke to upset and weaken the potency created by the combination of the undisturbed mixture of the gases and cancerproducing solids. Also, it is desirable to filter the tobacco smoke in a manner which will prevent the passage of as many of the harmful constituents thereof as possible while still allowing passage of at least some of those components, such as nicotine, which are recognized as sources of tobaccos unique taste and flavor and which are relatively safe.

According to the present invention, it has been found that the white variety of a nonmet'allic mineral, classed as vitric glass, has suprisingly superior qualities for the effective filtration of tobacco smoke when mounted in the draw path of the tobacco charge, consistent with the objective of removing harmful irritants and gases, without degrading the desirable taste and ffavor derived from the tobacco smoke. This material has typical percent by Weight chemical analysis as follows:

Silica, SiOz 69. 32 67. 36 69. 96 65. 24 67. 36 Iron oxide, Fem-.-" 2. 40 0.88 24 0. 48 Aluminum oxide, A1 0 20. 27 14. 88 16. 98 15. 22 14. 88 Calcium oxide, Cat) 2.05 1. 40 0. 64 2. 10 1. 40 Magnesium oxide, MgO 2. 06 0.48 2. 9 72 48 Potassium oxide, K 0 2. 50 4. 10 0. 09 2. 25 4. 10 Sodium oxide, N830 3. 05 2. 84 2. 25 3. 05 Lglss of ignition NIH 7.82 10. 12 7. 82 p Generally the vitric glass comprises at least 60% silica with the silica and aluminum oxide total being greater than 75% and the balance being essentially alkaline earth and alkali metal oxides. Other materials such as fiavorings or coolants can, of course, be added to the mixture for use as a filter.

This material is inert chemically to the smoke filtered and imparts no significant taste or odor thereto. The use of the material results in an extremely smooth and nonirritating smoke. The material is not harmful if accidental- 1y swallowed or inhaled, and is nonfiammable. When subjected to fourteen hundred degrees Fahrenheit, it was found to be noncombustible and emitted no detectable odor. These latter attributes are substantially beneficial when the material is used as a cigarette filter because the filter then enables the cigarette to be self-extinguishing when the tobacco burns to the filter and thus results in a safer product from a fire hazard standpoint.

Accordingly, it is an object of this invention to enable more complete filtration of undesirable elements from tobacco smoke.

It is a further object of the present invention to provide an improved filter for tobacco smoke.

An additional object of this invention is to provide an improved filter for tobacco smoke, said filter including a mineral in a particulate form through which said smoke passes.

Another object of this invention is to enable improved filtration of tobacco smoke to be obtained by passing the smoke through an amount of vitric glass in particulate form.

These and other objects of the invention will be better understood upon a consideration of the following description taken in conjunction with the attached drawing in which:

FIGURES 1A and 1B illustrate an example of a filter according to the invention afiixed to a cigarette;

FIGURE 2 illustrates another example of a filter according to the invetnion atfixed to a cigarette;

FIGURE 3 illustrates a cigarette wherein the tobacco and filtration material according to the invention are intermixed;

FIGURE 4A is a perspective view of a single filter particle; and

FIGURE 4B is a perspective view of a single filter particle having minute filter particles thereon.

The preferred filter comprises a coarse forty-sixty mesh grind particulate vitric glass intermixed with ten to seventeen percent by weight of a four hundred and twenty-five mesh grind (fines). More broadly, however, the filter may be formed from all coarse twenty to sixty mesh particles or from an intermixture of coarse and smaller sized particles such as one hundred mesh, two hundred mesh, etc., up to four hundred and twenty-five mesh fines. The upper limit on the amount of smaller particles added depends only on the pressure drop through the filter. This should not exceed 15 cm. of water.

The particulate vitric glass may be formed by ball milling and screening. As used herein grind or mesh is used in a conventional sense to refer to the coarseness or fineness of screens through which particles of the ma terial pass and is expressed as the number of openings per linear inch. Thus, a forty-sixty grind (sometimes referred to as minus forty, plus sixty or through forty, on sixty) means that the material passes through a forty mesh screen, but does not pass through a sixty mesh screen. Similarly, a material of four hundred and twenty-five mesh passes through a four hundred and twenty-five mesh screen.

Various size vitric glass have been tried such as twentysixty and thirty-sixty grinds and all have been found to be satisfactory. Some are more satisfactory with pipe tobacco, however, for example the more coarse twenty-sixty and thirty-sixty grinds. Others, such as the forty-sixty grind, have been found more acceptable with cigarette tobacco. The forty-sixty grind with -17 of fines (through four hundred and twenty-five mesh) is preferred since this combination has the most effective filtration capabilities and has a smooth and easy draw which are acceptable commercially.

The preferred cigarette filter is typically approximately five-eighths inch long and includes the forty-sixty grind intermixed with 10-17% of vitric glass having a size of approximately four hundred and twenty-five mesh with about 12% moisture. It has been found, however, that a basic twenty-sixty grind can be used to produce better filtration than conventional filters. It has been observed that the reduction in total particulate matter and harmful gases is greater with such a grind than with the commercially available cellulose acetate filters, for example. These observations are more thoroughly illustrated by means of the following examples.

Example 1 A standard brand cellulose acetate filter cigarette was smoked to a 30 mm. butt on a conventional smoking machine. The reduction in total particulate matter of the 84 mm. length cigarette was 39.6% and the reduction in nicotine was 25.3%. In contrast, when a twenty-sixty mesh grind vitric glass was used as the filtering material for a cigarette of the same brand and length the reduction in total particulate matter was about 50% and the reduction in nicotine was greater than 30%. When smaller particulate vitric glass was added to the coarse grind mixture the percentage reduction in particulate matter and nicotine increased. Thus the addition of sixty-one hundred grind vitric glass material or two hundred mesh, three hundred mesh or fines, beneficially effects the filtering properties of the coarser vitric glass filter material.

to draw the smoke through the filter made this mesh im-.

practical from a smokers standpoint.

Example 3 A standard brand (Winston) king size filter cigarette of 84 mm. length was smoked to a 30 mm. butt with a conventional smoking machine on a Cambridge CM113A filter in accordance with the procedures recommended by the Federal Trade Commission. These standard conditions included a 35 cc. puif of two second duration and one minute frequency at a temperature of 75 F. and 60% relative humidity. The initial weight of the total particulate matter obtained from the cigarette with the filter removed was 41.7 mgs. The weight of nicotine was 1.78 mgs. The same cigarette brand was smoked with a standard filter under the same conditions. The total particulate matter was reduced to 25.2 mgs. and the nicotine to 1.33 mgs. (the Congressional Record of Nov. 28, 1967 lists the total particulate matter for this same cigarette at 20.4 plus or minus 0.05 mg. and the nicotine at 1.29 plus or minus 0.05 mg.).

A filter was prepared from a mixture of twenty-sixty grind vitric glass With about 10% fines (through four hundred and twenty-five mesh). This filter was mounted on the same brand cigarette with the regular filter removed and the observed particulate matter after smoking under the same conditions was 10.4 mgs. and the nicotine was .54 mg. The number of puffs to produce a butt length of 30 mm. was ten for both the standard filter and the vitric glass filter.

Example 4 A filter was prepared by mixing 16% fines (through four hundred and twenty-five mesh) with 84% of a fortysixty grind vitric glass. The filter was attached to the same brand cigarette with the conventional filter removed and the cigarette was smoked under the conditions listedin Example 1. The total particulate matter was 1.4 mgs. and the nicotine content was 0.10 mg.

The total particulatematter was reduced by the filter of Example 5 by 96.6% and 94.4% of the nicotine was removed. In contrast the standard cellulose acetate filter, as discussed, removed only 39.6% of the total particulate matter and 25.3% of the nicotine.

The effectiveness of a basic twenty-sixty grind of the particulate vitric glass is increased by the addition of any amount of smaller particles since a greater surface area for filtering is provided by the addition of the smaller particles and since the through passages are reduced by the smaller particles filling the interstices between the coarser grind material. The only upper limit on the number of smaller particles which are added to the basic grind appears to be the draw pressure through the filter material. This may be expressed in terms of the number of puffs (as defined by the conditions listed in Example 1) required to reduce the cigarette to a 30 mm. butt length. In Example 5 the number of standard puffs required for such a reduction in length increased to 10.6 bv the addition of the higher quantity of fines. For example, the number of puffs should be under 12 for comfortable smoking. A more preferable way to define the upper limit on the smaller particles in the filter, however, is in terms of the pressure drop across the filter. The pressure drop is that value obtained when the pressure differential between two points along the filter is determined. In the case of cigarette filters, it is the pressure difference between the two ends of the filter at a normal air flow of 17.5 cc./sec. at 75 F. and 1 atmosphere. The pressure drop is expressed in centimeters or inches of water. The beneficial filtering effect of adding smaller particulate vitric glass to the base twenty-sixty grind is obtained as long as the pressure drop through the filter does not exceed 15 cm. of water. More preferably, the amount of small particulate vitric glass should be low enough so that the pressure drop through the filter is less than about 12 cm. of water. For example the pressure drop through a forty-sixty grind filter, when the fines are about 17% by weight, is in the vicinity of 10-14 cm. of water. Most standard filters in present use fall within the range of 212 cm. of water pressure drop.

Color photochronograph studies made through microscopic equivalent revealed that the vitric glass material has such a minute nuclei that it is possible to create a porous material with apertures so infinitesimal that virtually nothing can be passed through the material, without undergoing a change in composition, when ten to seventeen percent of the extremely fine four hundred and twenty-five mesh material is added to the forty-sixty grind. The addition of the fines provides an appreciably lower porosity, and it has been computed that it expands the area of surface exposed for filtration to approximately sixty linear feet and significantly increases the volumetric mass. The tiny particles surround and cling to the larger particles or granules in a closely-packed and tenacious manner, thus essentially filling in all of the available space within the filter area in such a perfect geometrical pattern that all avenues of passage are effectively closed, allowing the smoke to pass only by being drawn through the very nucleus of each particle. It further has been estimated through computation that filtration of particles down to a fraction of a millecron is achieved. A millecron is defined as being one-millionth part of one micron or 39.37 x 10 inches. Thus any particle or composition of matter exceeding the micron size of nicotines chemical particulate nature is elfectually removed.

Example 6 A standard brand cigarette of 70 mm. length, with no filter, had a test yield of 30.5 mgs. per cigarette of condensate nonvolatile or combustion residuals. The yellowbrown condensate, tobacco tar, was collected in glass traps cooled to the temperature of liquid nitrogen and contained all of the particulate phase of the smoke as well as considerable components of the gas residuals. This residual was tested through the ultraviolet absorption spectrum as well as comparison being made of the fluorescence spectrum and a mass spectrometry test on a sample collected from the identical untreated tobacco. By using a forty-sixty grind with 10% of the four hundred and twenty-five mesh, the yield of residuals was reduced from 30.5 to 3.286 mgs. per cigarette. The harsh gaseous elements were removed, eliminating coughing upon deep inhalation without diminishing the enjoyment, taste or aroma of the tobacco. Conventional cigarette filters for this brand and length normally provide a reduction in tars from the usual unfiltered yield of 30 mgs. to approximately 20 mgs. In addition, it was found that the temperature of the smoke passed by the filtered material according to the invention was at or below room temperature, and this filter material has isothermic properties.

Example 7 Subsequent tests also have shown a substantial reduction in tarry residue. Again, a well-known brand of filter cigarette was used for all tests. Tests Were made by first removing the conventional filter to obtain the total quantity of tars from an unfiltered cigarette. The cigarette was placed in a vertical position in a short length of glass tubing. The glass tubing was connected to a cold trap where the tars and combustion products were collected. The same length of tobacco was consumed for each test, and the same draw vacuum was used for each test. The entire assembly was first weighed, and then weighed again after drawing the smoke through it from the cigarette. An unfiltered cigarette yielded 85.4 mgs. of tarry residue. Using the conventional filter for the cigarette, 42.6 mgs. were collected. Using a filter material of a forty-sixty grind and 10% four hundred and twenty-five mesh according to the present invention, only 2.2 mgs. were collected. Based upon the unfiltered cigarette as a one hundred percent reference, the conventional filter removed 50.1% of the tarry residue while the filter material according to the present invention removed 97.42%.

The temperature of the smoke in Example 7 was determined by a thermocouple inserted into the glass tube which held the cigarette. The unfiltered cigarette smoke reached a temperature of F. within thirty seconds and a final temperature of 140. The normal filter smoke reached a temperature of 106 in thirty seconds and a maximum temperature of at the end of the test. Smoke filtered through filter material according to the present invention dropped in temperature from 74 to 72 during the first thirty seconds, and gradually rose back to a temperature of 74 which was maintained until the end of the test.

A filter using filter material as described herein was used on conventional plain and mentholated cigarettes, and smoking of these cigarettes showed only very slight changes in flavor and an extremely smooth and nonirritating smoke.

In all of the examples the gas phase contents of hydrogen cyanide and acrolein, both considered harmful, were reduced appreciably. This was believed to contribute to the uniformly recorded smoothness and non-irritability of the smoke drawn through the filter. The isothermic prop erties of the filter were also always observed.

Inasmuch as nicotine is not considered harmful but does contribute to the taste and aroma of tobacco smoke, it is preferably to allow at least a certain amount thereof to pass. It has been found preferable not to activate nor to calcine the vitric glass because the normal moisture content of 12% in the vitric glass prevents the absorption of many of the oils contributing to the flavor while the microscopic passageways effectively prevent the passage of any particles or solids exceeding the size of the nicotine particles. The amount of nicotine passed thus can be controlled by the moisture content of the filter material, with a lower moisture content preventing the passage of more nicotine. The 12% moisture in the filter material also co-i incides with the amount of moisture usually found in tobacco" and does not dry out tobacco during storage and prior to smoking.

ter mixture, and this is dependent upon the amount of nicotine present in various tobaccos. About 2 grams of the twenty-sixty or forty-sixty mesh along with 10'17% of the four hundred and twenty-five mesh dust has been found preferable for the average cigarette. Because pipe tobacco and cigar tobacco containa great deal more nicotine than cigarettes, coarser meshes of twenty-sixty and thirty-sixty grind are preferred because of the capacity'of the larger particles to absorb more particulate matter, and the percentage of the smaller mesh particles such as the one hundred, two hundredand vfour hundred and twenty-five mesh size particles typicallyis increased up to 17% but not sufficiently-high to cause the pressuredrop through the filter to exceedfcm. ofwater. p

FIGURE: 1A illustrates a cigarette 10 .having a paper wrapping 11 and tobacco 12 v therein. An amount offilter' material 13 according to this invention is.retained in a conventional paper filter sleeve 14 attachedto thewrapping 11. A small amount ofvcellulose acetate or.,c0tton 15, which may be the sameas the filter material used in conventional cigarette filters,-is. employed to retain the filter material 13 within the sleeve" 14. FIGURE 2 illustrates a similar cigarette 17, paper sleeve 18 and filter' material 19 according to the present invention. In this invention may be mixed with tobacco 23.to form'a -ciga-- rette 24, but this has not been'found as satisfactorybe cause the smoke is not cooled aswell as in the arrange-i ment shown in FIGURES l-or 2. A small amount, such as 2 grams, of the material may be used in the bottom of a pipe bowl before the tobacco is inserted. FIGURE 4A is a greatly enlarged illustration of a single particleof forty-sixty grind material according to this invention, and FIGURE 4B illustrates a similar particle and shows the general manner in which the dust or tiny particles 26 cling thereto. 1

The present embodiments of this invention are to be considered in all respects as illustrative and not restrictive.

What is claimed is: 1. A tobacco smoke filter comprising a coarse particu-.v late twenty-sixty mesh size vitric glass intermixed with an efiective amount of smaller particles ofthe same material so that the detectable combustible residuals passing through, said filter are reduced and the pressure drop through said. filter is less than 15 cm. ofwater.

2. A tobacco smoke filter as defined in claim 1 wherein the amount of saidusmaller particles is effective to maintain the pressure drop through said filter below 12 cnn of water. v t v 3. A filter as defined in claim 1 wherein said twentysixty mesh size particles are surrounded bysaid smaller particles, said smaller particles adhering thereto to form a distribution of small and large'particles in the filter in .a geometric pattern which closes.all space so that any particles. exceeding the size of nicotine are removed from said tobacco smoke passing through said filter and wherein the amount of said smaller particles is less] than *theamount of smaller particlesrequired to increase the pressure.drop through said filter above 15 cm. of water.

4 4. A tobacco "smoke filter as defined in claim 1 wherein said vitric glass comprises at least 60% by weight silica and has a total silica and aluminum oxide content'of, greater than by weight, Ilie balance being essentially alkaline earth and alkali metal oxides.

5.'As a tobacco smoke filter'a sfdefined in claim 1 wherein said coarse particulate vitric glass is forty-sixty mesh size and said smaller particlesj'cornprise 10 to 17% of extremely fine particles of vitric'gla ss; I

' 6. A filter as in claim 5 wherein saidglass has 13, moisture content of approximately 12%., v r p i 7. A.filter as in claim 5 wherein said extremely fine particles have a meshv size 'of approximately four hundred andtwenty-five. I

[8; A filter for tobacco smoke comprising twenty-sixty mesh particulate vitric 'glass'mounted in the path of draw of the tobacco charge." v

9. A filter as .defined in claim 8 wherein the-chemical analysis of said vitric glass comprises silica, iron oxide, aluminum oxide, calcium oxide, magnesium oxide and potassium oxide and said vitric glass has a pH of about 7.

10. In a tobacco smoke filter, particulate vitric glass having a twenty-sixtymesh size intermixed with 10 to 17 of approximately four hundred and twenty-five mesh size particles of vitric glass.

' 11. A method of filtering tobacco smoke comprising passing the majority of said smoke through a mixture of large and small particles of vitric glass wherein said large particles are approximately, twenty-sixty meshsize and the pressure drop through said mixture is less than 12' cm. of water.

References Cited UNITED STATES PATENTS 1,985,840 12/1934 Sadtler 13 l-10.9" 2,313,648 3/1943 Lavietes l3l187 2,765,515 10/1956 Knudson 131-10.9 X 2,768,913 10/1956 Hiler 13 l10.9 2,786,471 3/1957 Gr'aybeal 131l0.7 2,806,474 9/1957 Yarsley 131-265 2,916,038 12/1958 Wade H .Q 131-267 3,039,908 6/1962 Parmele 131-267 X 3,049,449 8/1962 Allegrini l3 l17 3,117,580 1/1964 Weisman 131-l7 X SAMUEL KOREN, Primary Examiner D. I. DONOHUE, Assistant Examiner us. Cl. X. R. 131-101, 17 

